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Agents Pore Over Suspect’s Trip to Russia

F.B.I. agents are working closely with Russian security officials to reconstruct Tamerlan Tsarnaev’s activities and connections in Dagestan during his six-month visit last year, tracking meetings he may have had with specific militants, his visits to a radical mosque and any indoctrination or training he may have received, law enforcement officials said Sunday.

At the same time, the bureau is also still looking for “persons of interest” in the United States who may have played a role in the radicalization of Mr. Tsarnaev, 26, and his younger brother Dzhokhar, 19, before the Boston Marathon bombing on April 15, Representative Mike Rogers, Republican of Michigan and chairman of the House Intelligence Committee, said on ABC News’s “This Week” on Sunday. But Mr. Rogers said “the big unknown” remains what happened in Russia.

Investigators believe it is likely the Tsarnaev brothers were self-radicalized and got their bomb-making instructions strictly from the Internet. But they are still exploring the possibility that other people in Russia or the United States were critical influences, if not accomplices, and officials say it may be weeks before the full picture of their plot is clear.

Officials said they were still examining the conduct of the Tsarnaev brothers’ mother, Zubeidat Tsarnaeva, and Tamerlan’s wife, Katherine Russell, 24, who converted to Islam when she married him in 2010.

On Saturday, the Russian investigative newspaper Novaya Gazeta reported that Mr. Tsarnaev had sought to join the Muslim insurgency in Dagestan and had been in contact with several rebels who were killed by Russian authorities in late spring of 2012 while he was staying in Makhachkala, the regional capital. Mr. Tsarnaev left Dagestan in July 2012, just two days after a shootout between militants and the police in which several militants were killed, including William Plotnikov, 23, a Russian-born Canadian. Investigators are trying to determine whether Mr. Tsarnaev and Mr. Plotnikov met, one official said on Sunday.

In 2011, Russian officials sent a warning about Mr. Tsarnaev’s extremist views to both the F.B.I. and the C.I.A., saying they believed he was coming to Dagestan, a republic in southern Russia, to connect with underground groups. That warning was based on telephone conversations intercepted by Russian intelligence, including one between Mr. Tsarnaev and his mother, in which they discussed jihad, Russian authorities have told the F.B.I.

Experts on the effort by Russian authorities to contain the Muslim insurgency in Dagestan and elsewhere in the North Caucasus region said that if officials were aware of Mr. Tsarnaev’s arrival in Dagestan in January 2012, he probably would have been under scrutiny throughout his time there.

“He would have been flagged at the airport, when he entered Dagestan and when he went to the mosque,” said Jean-Francois Ratelle, a Canadian scholar at George Washington University who is studying the insurgency in Dagestan. Mr. Ratelle said that in his own research trips to Dagestan, he had been stopped almost every day on the street by police officers checking his registration papers, in part because he has a beard, which is seen as a possible sign of religious devotion.

It is unclear how closely the police were tracking Mr. Tsarnaev, but his mother described at least one instance in which her son was stopped by the police along the beach in Makhachkala, where Mr. Tsarnaev’s parents live, and brought in for questioning.

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“He’s like: ‘The police came there and they asked for documents,’ ” Ms. Tsarnaeva said at a news conference last week. “They asked him to follow. He was asking them, he was like in shock. He’s like: ‘What, is there something wrong with me? Am I strange, or don’t look like everybody?’ ”

At the news conference, the brothers’ father, Anzor Tsarnaev, acknowledged that Mr. Tsarnaev had occasionally prayed at a mosque on Kotrova Street in Makhachkala that is known as a gathering spot for some Salafists with extremist views. The mosque is just a short walk from the soccer stadium for the local Dynamo team. Graffiti, written in stark red on a white wall nearby the mosque says, “Victory or paradise.”

In an interview, the imam at the Kotrova Street mosque, Khasan-Khadzhi Gasanaliev, said he had never met Mr. Tsarnaev, and none of the men interviewed outside the mosque over the course of several visits said they had known him. Videos posted by Mr. Tsarnaev indicate that he was familiar with Muslim rebel leaders in Dagestan, and investigators have been seeking to determine if he met with any of them in person.

The account in Novaya Gazeta said that one of Mr. Tsarnaev’s contacts was Mahmoud Mansur Nidal, who was killed on May 19 after a standoff with Russian authorities at an apartment house in Makhachkala. Surrounded by Russian security forces, Mr. Nidal took several hostages, according to the news agency Interfax, and at one point threw a grenade at the authorities. The hostages were released after some negotiation, but Mr. Nidal refused to surrender and was shot dead, Interfax reported.

Another possible contact was Mr. Plotnikov, a Russian émigré to Canada who became disenchanted with life there, converted to Islam and then moved to Dagestan to join the Muslim insurgency. He had been trained in boxing by a well-known Russian coach in Canada and was known among the Muslim rebels in Dagestan as “The Canadian.” Mr. Plotnikov became a member of the Mujahideen of the Caucasus Emirate and had briefly been detained by Russian authorities.

Law enforcement officials have said that the marathon bombs were constructed largely according to instructions in Inspire magazine, a publication of the Qaeda branch in Yemen. But Representative Michael McCaul, a Texas Republican and chairman of the House Homeland Security Committee, said on “Fox News Sunday” that “the level of sophistication” of the homemade pressure-cooker bombs used at the marathon “leads me to believe that there was a trainer.”

Mr. Ratelle, the George Washington University scholar, said most militants in Dagestan “see the U.S. as an enemy of Islam.”

“But it would not be their main target,” he said. “They wouldn’t be likely to provide training for an attack on the U.S.” The Caucasus Emirate has denied any role in the marathon bombing.

Andrew Roth and Ian Austen contributed reporting.

A version of this article appears in print on April 29, 2013, on Page A10 of the New York edition with the headline: Agents Pore Over Suspect’s Trip to Russia. Order Reprints|Today's Paper|Subscribe